In the past, there has been developed a technology in which when a three-dimensional or solid object existing ahead of an own or subject vehicle is detected and a collision between the solid object thus detected and the subject vehicle is predicted, brakes are electrically operated so as to avoid the collision of the subject vehicle with the solid object by means of a braking force. However, only with the collision avoidance due to the braking force, there may occur a variation in the generated braking force depending on the condition of a traveling road surface or the state of tires, and in addition, such breaking may become a factor which causes sudden braking. As a result, there is developed a technology in which an avoidance operation is carried out by means of turning motions, in cases where sufficient collision avoidance can not be attained with the braking force (for example, see a first patent document).